The rotator cuff is a confluence of tendons that connect the muscles originating around the scapula and inserting on the upper humerus. When activated, these muscles raise, lower, and rotate the arm. The rotator cuff tendons measure about 5 cm in width, on average, and together they form a cuff that encapsulates the article surface at the top of the humerus. The acromion (the bone on the top of the shoulder) forms a bony and ligamentous arch over the rotator cuff and is bordered by the acromioclavicular ligament, the coracoid (the bone in front of the shoulder), and the acromioclavicular joint.
The rotator cuff can be inured by a number of different mechanisms. For example, if a person falls and lands on his shoulder, the acromion can strike the rotator cuff causing injury to the muscles or tendons. The extent of the injury, which can be either a bruise or tear, depends on the position of the arm during the fall, the strength and flexibility of the muscles and tendons, and the geometry of the undersurface of the acromion.
When the cuff is bruised, bleeding into the tendons may occur, and the tendons can swell, causing the cuff to be compressed, given the relative narrowness of the space provided for the cuff. This condition may persist for some months and is typically characterized by weakness and pain, especially when the outstretched arm is raised to the side or rotated. Symptoms are usually self-limited after appropriate treatment.
A torn rotator cuff is a significantly more serious problem. Symptoms are similar, although nighttime pain is often more intense, and the ability of the muscle to move the arm is significantly weakened, resulting in limited motion. If the condition does not stabilize over time with rest and supportive care, surgery is often recommended (especially in cases where the cuff tear is significant, and/or in order to prevent the development of osteoarthritis). The size of the tear is typically determined using an arthrogram or by MRI.
While the surgical repair has historically been performed as an open procedure (and more recently as a “mini-open” repair), the majority of rotator cuff repairs are now repaired fully arthroscopically, with the tendon being reattached directly to the bony insertion on the laterial borer of the humerus. However, when direct reattachment is not possible, for example, because retraction of the muscle has created a large defect, interposition devices or grafts (including synthetic cuff prostheses) are used to fill the defect. Devices (or grafts) are also used as augmentation devices to strengthen a repair to prevent recurrent tears and allow for a more aggressive rehabilitation particularly in younger patients.
Autologous grafts, including tendon, muscle and fascia lata are all used in rotator cuff repair (Ito, J. and Morioka, T. Int. Orthop. 27:228-231, 2003). Biologic and synthetic prosthetic grafts, which avoid the morbidity associated with the use of an autograft, are also used to repair rotator cuff injuries and include, for example: freeze-dried rotator cuff allografts, PTEF felt (marketed by Davol Inc.), carbon filament (Mura, N. et al. Clin. Orthop. 415:131-138, 2003); and more recently, the RESTORE® Orthobiologic Soft Tissue Implant manufactured from small intestine submucosa (marked by DePuy), the GraftJacket™ manufactured from decellularized dermis (marketed by Wright Medical), the TissueMend® manufactured from collagen (marketed by Stryker Orthopedics), and the Zimmer® Collagen Repair Patch manufactured from chemically crosslinked, acellular collagen.
Notably, despite the fact that the majority of repairs are now performed arthroscopically, and that recent reports indicate a high percentage of recurrent defects after arthroscopic repair of large and massive rotator cuff tears in particular, there is currently no interposition or augmentation device that has been designed specifically for arthroscopic rotator cuff repair (Galatz, I., M. et. al., J. Bone Joint Surg. Am. 86-A:219-224, 2004).
It is estimates that approximately 250,000 rotator cuff repair procedures are performed each year to alleviate the persistent pain and discomfort associated with shoulder injuries, and help patients regain full range of motion. There is thus a significant need to develop interposition and augmentation devices to fill a defect or augment a repair that can reduce the percentage of recurrent defects. There is also a need to develop interposition and augmentation devices that can be delivered arthroscipiclly.
It is therefore an object of this invention to provide new medical devices for rotator cuff repair that can be used as interposition or augmentation devices wherein the devices have one or more of the following features; high initial strength, prolonged strength retention in vivo, sufficient mechanical properties to provide support for the surgical repair, flexibility, anti-adhesion properties, favorable tissue response upon implantation, degradation in vivo to a natural metabolite, minimal risk for disease transmission or to potentiate infection, capacity to remodel in vivo into healthy tissue, and/or sufficient material strength to prevent suture pull out or failure if other fixation is used.
In is another object of this invention to provide methods for fabricating interposition and augmentation devices for rotator cuff repair as well as other tendon and ligament repairs.
It is yet another object of this invention to provide methods for delivering the interposition and augmentation devices for rotator cuff repair, and generally for other tendon/ligament repairs, specifically including arthroscopic methods of delivery.